Immunoassay reagents and methods for detecting brequinar and analogs

A hapten having the formula:

• ##STR11## wherein:
• R is ##STR12## X is O, S, NR.sup.7 or CH.dbd.N;
• R.sup.1 is alkyl of 5-12 carbon atoms, alkenyl of 5-12 carbon atoms, cycloalkyl of 3-7 carbon atoms, cycloalkylalkyl of 5-12 carbon atoms, phenyl substituted with 0-3 Y, or benzyl substituted with 0-3 Y;
• R.sup.2 is phenyl substituted with 0-3 Y, or benzyl substituted with 0-3 Y;
• R.sup.3 is H, alkoxy of 1-3 carbon atoms, alkylthio of 1-3 carbon atoms, or alkyl of 1-2 carbon atoms;
• R.sup.4 is COOH;
• R.sup.5 is H, F, Cl, Br, I, CH.sub.3, CF.sub.3, S(O).sub.n R.sup.8 or ethyl;
• R.sup.6 is (CR.sup.9 R.sup.10).sub.p CH.sub.2 NH.sub.2 ;
• R.sup.7, R.sup.8, R.sup.9 and R.sup.10 are independently H or alkyl of 1-3 carbon atoms;
• Y is selected independently at each occurrence from the group consisting of:
• H, F, Cl, Br, alkyl of 1-5 carbon atoms, NO.sub.2, alkoxy of 1-5 carbon atoms, alkylthio of 1-5 carbon atoms, OH, CF.sub.3 and NH.sub.2 ;
• m and n are independently 0, 1 or 2;
• and
• p is 0-12;
• or a suitable salt thereof.